Some common middleware used in everyday application development in Koa includes the following:

• koa-router: RESTful resource router for Koa
• koa-connect: For mounting connect/express middleware
• kcors: For CORS support
• koa-body: For parsing HTTP request body
• koa-logger: Development style logger for Koa

A comprehensive list of supported middleware can be found on Koa's middleware wiki.